1. Field of the Invention
The invention relates to a foldable intravascularly insertable blood pump comprising a rotor provided with vanes, a flexible shaft extending through a catheter and adapted to drive the impeller, and an envelope enclosing the impeller.
2. Description of Related Art
Rotary blood pumps are known which are inserted into the heart for supporting the pumping capacity of the natural heart. Insertion is performed intravascularly, namely through the blood vessel system of the patient. It is thus required that, upon insertion, the maximum diameter of the blood pump does not exceed 3 mm, if the insertion is to be carried out through an insertable tube and with as little complication as possible. Further, the blood pump should be flexible for the purpose of conforming to the bends of the vessel course.
An intravascularly insertable flexible blood pump which forms the basis of the first part of claim 1 is described in WO 99/44651. The blood pump is a self-unfolding pump and comprises a flexible compressible envelope in the form of a tube which defines the pump housing. In the envelope a radially compressible rotor is arranged. The rotor is configured as a helix driving the blood flow in axial direction. The drive shaft of the rotor extends through a catheter. The catheter, together with the housing and the rotor, can be drawn into a tube sleeve. In such an axial pump the requirements concerning dimensional accuracy of the axial pump are relatively high. The rotor must conform, within close tolerances, to the inner shape of the housing for the purpose of attaining a flow rate of at least 2 l/min. (liters per minute) at physiological pressure conditions and without excessively destroying blood. These requirements are difficult to fulfill with a foldable blood pump. The axial pump must be operated at a relatively high speed of 30,000 to 35,000 rpm.